Irresistibly Contagious
by Xanoka
Summary: Beacon Hills Memorial Hospital needs a Santa for all the sick kids and the Hale Pack is pressed into service, with Derek in the starring role. Stiles is supportive. That is definitely the word for it. Christmas themed fluff inspired by the true story of my friend's experience as a Santa. The title is a shameless pun. Rated for mild swearing and innuendo.


_There is nothing in the world so irresistibly contagious as laughter and good humour_

 _A Christmas Carol,_ Charles Dickens

* * *

"I can't believe they roped you into this!"

Dang. He'd been aiming for sympathy, but that definitely came out way too gleeful.

Derek just glared as balefully as he could from under the Santa hat, perched jauntily on his head by a helpful elf.

"You could, at least, try to be supportive." He didn't so much speak, as his voice emerged from the bushy fake beard, like a deranged explorer stumbling out of the jungle. Which. Hilarious. And unfair!

"Dude, I am _being_ supportive. It's literally my job description. Like, 'Santa's Helper' supportive." He gestured down at his adorable holly green elf costume. The movement sent all the little bells he'd painstakingly sewed onto his costume a-jingling, and a vein in Derek's forehead a-throbbing with every merry peal.

 _When the Red Vein's throbbin'_

 _Get hop hop hoppin' along, aloooong._

Heh.

Hilarity, thy name is Stiles.

Not something Derek would probably appreciate right now. Though, it's not like he could resist humming a few more bars. And a little, bell enhanced spin.

"Man, where's Scott? I'm Christmas _personified_ right now."

Derek's glower only deepened.

And, OK. It was a little corny. And, like the rest of the Beacon Hills Memorial Hospital's Christmas supplies, the costumes are kind of well-used. And musty smelling. The pack had bitched _so much_.

Because, of course, if Derek had to be Santa, there was no way the rest of the pack wasn't going down with him.

But, hey. _Christmas_. Sick children. Who would say no to that?

A monster, that's who. And not the Creature of the Night variety, either.

(Except for, maybe, vampires. Because fuck vampires, those guys are assholes.)

"I guess I should be grateful you didn't inflict those things on anyone else."

Stiles gasped in not-entirely-fake outrage.

"What are you saying about my totally awesome costume modifications? I spent hours adding these. Bells are hella Christmas. They bring Christmas _joy_ , Derek."

"Christmas _misery_."

Stiles narrowed his eyes.

"I'll weave them into your beard, don't think I won't."

Derek probably smirked. It was hidden under the oodles of beard, but clearly audible.

"Too late! Santa comes but once a year. Too bad."

Stiles snorted and bit his lip. To go there or not to go there? Hmmm.

Derek's eyes promised murder. Festive murder. Beaten to death with a giant candy cane kind of murder.

A sticky end.

Oh God.

Distraction! Use the words, Stiles!

"Yeah. And like you won't be right back here next year." Good save. "No one can resist the McCall Puppy eyes!"

"Scott - "

"I'm not talking about Scott. Hah! _Scott_! No, I'm talking about _Melissa_. Where do you think Scott gets them from? Lethal, dude. Trust me."

A nurse hustled by in pink scrubs. Right. Paediatric Ward.

"Not to mention the kids! Can you really say no to the kids, Derek? Nah. You'll be back. And I'll be ready. Seriously, Derek. You'll sound like a children's carol singing posse. On sugar. Doing 'Jingle Bells.'"

Derek, being Derek, had to front.

"You wouldn't."

Ha!

"It's Christmas, dude. A stressful time for everybody over five. Don't tempt me."

There must have been something extra manic in his eyes. Or maybe the opening strains of _Walking in the Air_ cracked the facade, because Derek sighed deeply. Which was Derek for surrender. And yes! Definitely a good feeling! Big Bad Wolf: Zero. Christmas: Eleven. Santa's Elves for the win!

"Ha! Today's a great day! I'm marking it in my calendar!"

"You're insane." But there was fondness under the growling. For sure.

And Derek definitely carefully adjusted the stack of presents next to him for a better photographic angle.

"Awww, you love all this Christmas crap, really."

Strangely enough, he actually tensed, like he'd been caught doing something illicit. Which was a strange look on a guy who used to brazen his way through crime scenes, back when Stiles was still in high school.

"Awww, babe! You do!"

Derek growled. And, with all the beard, that was weird.

Although. How would wolfed-out Santa look? Like a Schnauzer, maybe? Except with less eyebrow action? A Bearded Collie?

He was about to ask Derek for his thoughts on it, but the sight of him clenching and unclenching his fist, while glaring a hole into the floor completely derailed that train of thought (Destination: Future Experimentation with Scott).

It was the classic Derek About To Talk About His Feelings pose, and always looked like he was giving himself hives.

But as the entire history of their acquaintanceship (and werewolves) had taught him, pain was gain. And Derek needed a little more gain.

So, Stiles slid himself onto Derek's lap, taking his hand as he did so.

"Hey, buddy, don't hurt yourself. C'mere."

Luckily, Derek relaxed his fist and let him thread their fingers together. Which was just as well, as the last time Stiles had tried alternative solutions to the Steely Tension of Tense it Did Not End Well.

(There had been tickling and broken furniture.)

"I do like Christmas," Derek announced eventually, low and guilty, like he was at confession.

And, figured Derek would feel guilty for enjoying Normal People Stuff.

Though, to be fair, their little Christmas grotto was, essentially, an enclosed pseudo-Christian booth. With the multicoloured lights blinking down on them, like the Eyes of God.

Or was that Dr. Eckleburg? Big Brother?

"My Dad," Derek began, saving Stiles from his literary angst. "My Dad - He, uh, used to dress up. As Santa. At Christmas."

"Oh, yeah?"

"Yeah."

The beard hid most of his face, and the lights made weird, distracting patterns, like they were inside a kaleidoscope, but he was definitely smiling his Patented Derek Smile which, unlike his daily stash of Poker Face, smirks and scowls, only came out to play on special occasions.

And something warm filled Stiles up, from his stomach to his chest. And it definitely wasn't the eggnog he had earlier.

"My Dad did the same," he admitted, in the Spirit of Shared Information. "My Mom too some years. 'Cos, you know, no sexism en Casa Stilinski."

Derek did his huffing-like-a-dog laugh, which always kind of made Stiles want to coo.

"I bet Melissa did too."

"Dude, did she ever! I swear, Scott used to get so confused with the Mall Santas. Like, who are these white dudes, and where is the True Hispanic Santa?"

"In drag."

"Well, duh."

Derek laughed quietly and Stiles grinned in triumph.

"You know," Derek said, because he was nothing if not abrupt. "My Dad used to say I'd do this one day -"

"Dude, living the dream!"

"Don't interrupt. He meant for my little brothers and sisters and cousins. And, uh, for my kids. One day."

The tip of his ear that Stiles could see peeking out from under the hat was burning red and he was glaring fixedly at the plastic Christmas tree in the corner, like it was about to commit a crime.

Stiles took a moment to process.

"Babe, are we having the Kids Conversation while I'm sitting on Santa's knee?"

" _No._ God, Stiles."

He tried to growl, but it came out more like a terrier wheezing. It was the sound of the Commitment-loving-Werewolf-Dates-Fickle-Human Panic, familiar from their early dating history.

How it had not been missed.

"Because, you know, this is opportune, babe. If we're talking Christmas Wishes. _Future_ Christmas Wishes, dude. Like Ghost of Christmas Future future. Except, I hope neither of us will be dead. Because I love my Dad, babe. He's awesome. And Melissa's basically a super hero. But I am not ready to be a single parent. Why am I talking about this? This is completely – But I'm still talking. Why am I still talking, Derek?"

Fortunately, Derek was a pro at ploughing though bewildering nonsense with a mostly straight face. It was why they worked so well together.

(Plus, a big part of why he was still alive. Stiles liked to think he helped hone that Cutting Through the Crap life skill, like a virtuoso's daily practice on their violin.)

(Play me like a fiddle, Derek)

"Stop talking, Stiles," he said reflexively, a defence mechanism for the both of them.

Stiles stopped.

"But, really. You want them. One day?"

"Well, I also want my two front teeth and a new engine for the jeep, but yeah."

Derek didn't say anything. Instead, he leaned in to nuzzle at Stiles' neck, which would have been awesome except -

" _Dude_ , beard!"

He tried to squirm away, but Derek held on, and this was payback for the Great Tickling Fiasco of '21, wasn't it?

But Christmas Spirit smiled on Stiles and Melissa arrived with a jingle.

Awesome, she had attached a bell to her hat.

"You're still the most awesome Santa," Stiles blurted.

She raised a sardonic eyebrow.

"It looks like you've replaced me."

"Oh, no," Derek said from over Stiles' shoulder. "You're still the One True Santa."

She quirked a smile at that, then clapped her hands, suddenly businesslike.

"Right, well. Get up, Stiles. The kids will be arriving soon."

"Hey, starting early? Kinky. Do I get a turn?" Erica smirked at them, appearing silently behind Melissa. Because she was a heathen and had forsworn the little package of bells Stiles had left her for costume edification purposes.

Stiles scowled and flung his arms around Derek's neck. Not that he was bitter about the bells, or anything.

"Back off, Reyes! This is a One-Elf Santa! Nobody rings his bell but me!"

"And that's one phrase I never needed to hear in any context, ever." Scott complained, arriving in Erica's wake. He stared hard at Derek for a second, then glanced at Stiles, who nodded slightly.

 _White Santa. Weird._

"Seriously, Stiles. Get to work. The children are arriving."

So he did, and they did.

And it was fun, and sad.

Most of the kids were visiting patients or staff in the hospital, or were, at least, mobile. Santa Derek and his Faithful Helpers, Elves Stiles, Erica and Scott would be touring the wards later.

And it was weird to see Derek talking to the kids. Adorable, yet surprising. Adorably surprising, like a koala attack.

Case in point.

"So what do you want for Christmas?" Derek asked for the nth time.

The little boy sighed loudly and looked away, even kicked his legs a bit from where he was sitting stiffly on the edge of Derek's knee.

"It's stupid. You won't care," he muttered eventually.

Derek glanced at them for help, and this was it, the heartbreaking moment a child asked for a miracle cure for Mommy. Stiles had been bracing for it all afternoon.

"Santa _always_ cares!" He said, a little too loudly and passionately.

"That's right," Derek agreed solemnly, like they were conferring on the fundamental laws of the universe.

The little boy mumbled something.

"Could you say that again, please?" Derek asked patiently.

The boy – "Calumn", a nurse had whispered loudly – glared at Stiles, like he was eavesdropping on a nuclear code exchange, then turned to cup his hand around Derek's ear.

"I like Transformers," he whispered, the loud and ticklish whisper of a preschooler, judging by Derek's face. He looked embarrassed to admit it, and, hey, Mini Derek.

Adult Derek was inscrutable for a second, then he bent his head and said, very seriously:

"I like Transformers too."

The kid gasped loudly.

"Really?" His face lit up, and he turned, scooting up Derek's lap to get closer. "Who's your favourite? I like Optimus Prime!"

Derek appeared deep in thought, like the fate of the world hung on his answer. It was his default thinking expression, and, man, was it having its time to shine.

"I like Optimus Prime too," he said eventually. "But my favourite's Bumblebee."

The kid nodded, like this was a respectable answer, despite said Transformer's obvious inferiority.

"Bumblebee's OK, he has nice colours," he said patronisingly. "But Optimus Prime makes this RAAWW noise and he's the bravest and he can be a tanker truck! And a dump truck!"

"Bumblebee can be a camaro though," Derek argued. "That's a sports car."

"And a Chevrowllay," Calumn agreed, dismissing Derek with an enthusiastic wave of his fist. "But! But! Optimus Prime can be a sports car too!" he practically shouted. "He can be a lamborheenee Deeablow!"

Derek appeared blindsided by this display of geek knowledge, and Erica took the opportunity to lean right into Stiles' space.

"Wow, he's like a Mini-Derek mixed with a Mini-you," she breathed, and Stiles nodded jerkily, not trusting himself to speak. If he did, there'd be tears, probably in the shapes of tiny little candy canes.

Scott patted his back with an amused expression.

"Like looking into the future, huh, bro?"

So he'd definitely been eavesdropping. Creepy werewolves.

But still.

Stiles nodded.

It totally was.


End file.
